Function CurrentScreen

CurrentScreen(): ReactNode
Render the current screen, overlays, and modals.

Multiple overlays are rendered in zIndex order (ascending) so higher zIndex overlays appear on top. Each overlay is wrapped in an OverlayContext.Provider so the keyboard system can isolate per-overlay keyboard layers by overlay ID.

Modals are rendered after overlays so they always appear visually on top. Each modal is wrapped in a ModalContext.Provider so the keyboard system can isolate per-modal keyboard layers by modal ID.

Architecturally symmetric between overlays and modals.

Returns ReactNode
Example
Render it as the leaf of the provider chain:
```
<ScenarioManagementProvider defaultScreen={MainScreen} fullScreen>
  <KeyboardProvider modes={['normal', 'insert']} mouse>
    <CurrentScreen />
  </KeyboardProvider>
</ScenarioManagementProvider>
```
- Defined in screen/current-screen.tsx:31